The engine operation in a hybrid electric vehicle (HEV) is significantly different than in a conventional vehicle as the vehicle may be operated using electric power only. In certain hybrids, such as plug-in electric hybrids (PHEVs), battery energy may be prioritized, and the engine may only run for a short time period during a vehicle operation cycle, or from key on to key off.
An HEV or PHEV with a diesel engine require emission control devices and corresponding control strategies for the devices. The diesel aftertreatment procedures or requirements may force more frequent and continuous engine-on operation. Examples of aftertreatment procedures include: diesel particulate filter (DPF) regeneration (Regen), catalyst light off, diesel oxidation catalyst (DOC) heat-up, other exhaust temperature maintenance procedures, and maintaining in-use monitor performance ratios (IUMPRs).
Energy management in a diesel PHEV favors reduced or minimum engine-on time to gain fuel economy benefits. For example, in a DPF Regen, additional fuel and engine-on time may be needed to complete the aftertreatment procedure. In a HEV or PHEV, the engine-on time is less than that of a conventional vehicle, and operating the engine for the purpose of completing an aftertreatment procedure leads to lower fuel economy for the vehicle.
There may be additional drivability concerns or expectations, like PHEV users, expecting the engine to be off when the power demand is low and the vehicle speed is low. The aftertreatment procedures need to be completed without significantly impacting fuel economy or drivability.